Pulse amplitude responsive selective system



y 7, 1953 5 A. ERICSSON ETAL 2,644,932

PULSE AMPLITUDE RESPONSIVE SELECTIVE SYSTEM Filed Dec. 7. 1948 2 Shets-Sheet 1 R7 R2 R3 R4 R5 R6 Fig.1

INVESNTQR$ ERIC AR ID mlczsscm a ERIK WAL EMBR B LLE GBRD :ANTON CjdRISTIBN JACOBBFLUS )BTTORNWS Patented July 7, 1953 PULSE AMPLITUDE RE SPONSIVE SELECTIVE SYSTEM Eric Arvid Ericsson, -Erik Waldemar Hullegard, and Anton Christian Jacobaeus, Stockholm; Sweden, assignors to Telefonaktieb'olaget L M Sweden, a company of Ericsson, Stockholm, Sweden Applicafim December 7, ,.S'erialNo. 63,875 In Sweden December 11, 1947 v j 4 Claims. '(Cl. 340-172) 1 In order to enable a telephone subscriber-to transmit the number of the subscriber, to whom he wishes to speak, to the automatic telephone 7 exchange to which he is connected, it must be possible to send over the subscribers line signals indicating the figures oi .saidnumber. This has, hitherto taken place by means of series of short interruptions-fo1lowing each other quickly-in a circuit from a central battery at the telephone, exchange, which circuit passes in a loop over the two wires of the subscribers line and comprises an impulse relay at the exchange. The interrup tions have been produced by means of a dial.

Attempts have been made to transmit necessary signals by means of change in a resistance in a circuit over the subscribers line. To this pur& pose, all the subscribers lines have, before the emission of the signal, been compensated to a definite resistance value and been connected in a balanceor bridge-connection, the influence of variations in the voltage of the exchange battery thus being eliminated. By means of push-buttons at the subscribers apparatus, difierent resistances have been introduced in the line circuit and been measured at the exchange by automatic setting of the resistance so that the balance has been maintained. change indicates the value of the signal.

The fact that similarsystemshave not yet been-used within automatic telephony is mostly due thereto, that it has not yet been possible to compensate ten difierentsettings with suflicient precision and speed. Rotary selectors move ionization of th'e'gas is obtained, can be kept up between them when they are connected to the" source of potential, and'on the other hand at least- The size. of the necessary I much too slowly, and relaychains with ten combinations cannot either 'follow the quick signal emission from a key set. 7 j

Nowadays a sufficient precisioncan be obtained at compensation of line resistances by meansof sensitive relays, and values.

The'object of the present invention to produce a sufliciently quick registration .of signals consisting of changes in the resistance on asubscribers line and produced by the keys in a key set. This is obtained, when the line circuit is closed over an adjustable resistance and is a part of abridge-connection comprising a receiving relay at the exchange, by saidreceivingrelay having a neutral intermediate position and two side-positions, in which the relay vactuates contacts closing circuits for the setting of an adjust able balance-resistance in said bridge-connection and automatically set by means ofspecial contact. devices, so that the balancing of the resistanceof the line circuit is obtained after. eachchang in; the resistance corresponding, to .a signal, whereby the size of the change indicates the signal.

tact k is closedand a circuit over'thesubscribers ,Due to the receiving -,1 e1ay having one intermediate position and two working positions, fixed processes are obtained as well at the beginning as at the endof each'signal; the value of the signal can simultaneously be read on the com-- pensating resistance necessary to restore the receiving relay to its neutral position.

The invention will be described more closely with reference to the accompanying drawings Figs. 1-2 showing diiferent embodiments of the invention.

Infig.v 1 an embodiment of the invention is shown, which is .intended for subscribers lines. Since only relatively small variations of the resistance'o'f the line circuit ariseat signaleniission by means of changes in the resistance on long subscribers lines, a great sensitivity of the receiving'devices is needed. This is obtained by means of aspecial discharge tube G2, comprising on one hand two electrodes, an anode A and-a cathode K, between which a discharge can be'protwo further electrodes E an'd J, to which the arc can be directed by increasing or respectively decreasing a magnetic field, over which further electrodes circuits for setting'o'f an adjustable balance resistance, TH-4'13, and r2 I- -r23 at the telephone exchange, are closed. I

It is especially important that "the balancing of the resistance of the subscribers line be adjusted with great carefulness. This is attained by suc'- cessive increase of the grid tension on an electron tube GI by charging a condenser connected to one of the grids of the electron tube until the anode current of the electron tube makes the arc dis-' charge in the above mentioned discharge tube take a neutral position betwen the two further electrodes E and J. To this purpose there are two helping electrodes F and D, over which a circuit for charging the condenser C is closed, when the arc discharge ionizes the gas 'onone'of' the spots between them. How'this'takes place w ll appear from the following description.

, At call from the telephone instrument T, conline is' closed. In a known Way, .which is not shownjin the figure, thesubscribers line "La'Lb" is thereafterconnected over a selector F V to a connecting links, ,which is bymeans 'oi'a con necting relay SI connected to" a register with a receiving device R. The relays SI-S3 and the talking wires a,b as well as two controlwires and d are all that is shown of the connecting link. When the contacts IIII-IO are actuated, a circuit is closed for relay R6 in the register by contact IOI. Relay R8 attracts its armature and contacts 6 I-65 are actuated. The following circuit is simultaneously closed: battery, contact 23I, 223 and 2I3, resistances rI I- 1'I3, winding on choke-coil D, contact I05, selector FV, line wire Lb, rectifier Re I resistance m, contact k, line wire La, selector FV, contact I03, re sistance T2 to negative battery. The resistance m can be varied by means of a keyset in the telephone instrument T. A voltage drop, which varies with the resistance of thesubscribers line, is obtained over resistance r2. When contact 62 is closed, the voltage +V3 is connected to the discharge tube G2, and an arc discharge takes place first between the ignition electrode B and the cathode K, which is indirectly heated, and thereafter, due to the voltage drop over resistance TB, between the anode A and the cathode K. The discharge tube G2 lies in a magnetic field generated by an electromagnet N. The condenser C is from the beginning charged with a certain tension, which is determined by the re sistances r3 and 14 and is fed to the condenser over contacts 6| and H. When contacts 6I--55 have been actuated and the arc discharge in tube G2 is lighted the electron tube GI has such a strong negative grid tension, that the anode current from the source of potential-I-VI does not noteworthily effect the magnetic field from the magnet N. The are discharge in tube G2 thereby takes place on the right side of the figure and a conducting connection is obtained between the electrodes D and F. The condenser C is thereby charged in the following circuit: The source of potential +V2, the electrodes D and F, resistance 15, contact II, condenser C, resistances TI and T2, to negative. As the condenser C is charged, the voltage increases on the grid in tube GI, and the anode current increases likewise and increases the field strength from magnet N so that an arc discharge in the discharge tube G2 is removed to the left on the figure. When the arc discharge has been removed so far, that it does not ionize the gas any longer between the electrodes D and F, the charging of the condenser C ceases. If thereby the grid tension in tube GI is still negative, the charging of the condenser and its tension will not change during the following connecting process.

When contact 65 is closed, the following circuit is closed: +battery, contacts H5, 65 and I3, winding on relay R4, to negative battery. Relay R4 attracts its armature. Contacts 4I--42 are actuated. Relay R3 attracts its armature. Contacts 3I--35 are operated. Relays R5 and R1 attract their armatures. Contacts 5| and 11-74 are operated. When contact II breaks, the charging of the condenser C must be completed.

The electrode F is thereafter disconnected by contacts 'II and 6 I, and the electrode J connected by contact I3. The are discharge is on the left side of the electrode F and touches either the electrode E or the electrode J. Relay R1 is selfbound over contact 12 in dependence of contact 64. A buzzer tone is connected from the buzzer generator Su over contact I4, winding on the choke coil D to +battery over wire t3. This circuit is broken in the register by the member which registers the first figure.

When the subscriber hears the buzzer tone, the

dialling can begin. Thereby a further resistance is connected in series with the line wires La-Lb, whereby the voltage over resistance r2 decreases. The anode current in tube GI decreases and therewith the field strength through magnet N. The are discharge thereby moves to the right in the figure and an electric connection is obtained between the electrodes D and J. The following circuit is closed: +V2, the electrodes D and J, contacts I3 and I I3, winding on relay RI I to positive. Relay RII attracts its armature and is self-bound over contacts 2I and III. Contact I I4 short-circuits resistance rI I, whereby the current strength on the subscribers line and the voltage over resistance r2 increases. If the increase of. resistance in the adjustable resistance m is thereby compensated, the arc discharge in the tube G2 moves again to its neutral position, and the current between the electrodes D and J is broken. If the short-circuiting of the resistance rII implies too little a decrease of the resistance, the arc discharge in the tube G2 will not break the electrical connection between the electrodes D and J, but the following circuit will be closed: +V2, the electrodes D and J, contacts I3, H2 and I23, winding on relay RI2 to +battery. Relay RI2 attracts its armature and contacts I2Il26 are actuated, whereby resistance M2 is also short-circuited. If this is not either suflicient, relay RI3 is operated, whereby resistance H3 is also short-circuited. Should, on the other hand, an over-compensation follow the short-circuiting of one of the resistances 7||- 113, e. g. when H I is short-circuited, the are discharge in the tube G2 will move past the neutral position, whereby an electrical connection is obtained between the electrodes D and E instead of between the electrodes D and J. The following circuit is closed: +V2, the electrodes D and E, contacts 33 and 2I6, winding on relay R2I to positive. Relay RZI attracts its armature. The contacts 8, 4, 9, 0 and 2II2I6 are actuated. Contact 2!3 connects the resistance 1-2I in series with the subscribers line, whereby the arc discharge in tube G2 moves to the right. If the move is not sufiicient for the neutral position to be reached. relay R22 also attracts its armature, whereby contacts I, 3 and 22I226 are actuated and resistance 122 connected. Relay R23 may possibly also be operated and contacts 6, 5, 2, I and 23I-233 actuated and resistance r23 connected. If we suppose that the Figure 2 has been dialled by the subscriber, the arc discharge in tube R2 reaches its neutral position, when resistance r22 is connected by relay R22.

When relay RI I actuates contact I I5, the current for relay R4 is broken, said relay then releases its armature with some delay due to a resistance being connected in parallel with the winding of the relay. In the same way relay R3 is somewhat slow-releasing. During the releasetime of relay R4, the setting of the relays RI I- RI3 and R2I-23 must take place. During the release-time of relay R3 the following circuit is closed for the registering of the figure: battery, contacts 42,34, II6, I26, H2, 222 and 2, if, as supposed above, the figure 2 has been dialled. From contact 2 there is a connection to the registering part of the register. When relay R3 releases its armature, the registering process must be over. Thereafter, no change takes place until the subscriber lets the pushed down button go. Should the slow-releasing relay R5 release its armature, this entails no change, since the arc discharge in tube G2 is at its neutral more closely.

position. "When the subscriber lets the pushbutton go, the balance is disturbed and the are discharge moves to the left, whereby the following circuit is closed: +V2, the electrodes D and E, contact 32, winding on relay R2 to positive. Relay R2 attracts its armature. Contact -2I is actuated, and the excitation circuits for the relays RI l-RI3 and R2I-R2'3 are "broken. Those of relays Rib-R13 and R2 IR23, which have been actuated, release their armatures, whereafter the balance'is restored again and the arc discharge in tube G2 remains in its neutral position. Contact H5 is closed again. Relays R4, R3 and R5 are operated and relay R2 releases its'armature.

Should the subscriber put down his microtelephone, the circuit over the subscribers line is then broken, the arc discharge in tube G2 remains on the right side even after the three relays RII-R'I'3 having attracted their armatur es. Relay RI receives current over contacts II2, I22 and 132. Relays R3-R5 releasetheir armatures. Relay RI attracts its armature, contacts II-I3 are operated and the following cir-.

cult is closed: battery, contacts II, 5|, I03, winding on relay .to negative over wire d in the connecting link S. Relay S3 attracts its armature, contacts I06I08 are actuated. The circuit for relay SI is broken. Relay SI releases its armature and the connecting link S is short-circuited from the receiving device R.

If the connecting process is pursued, the register will connect positive to wiret2 and shortcircuit the connecting link S. The current-feeding relay S2 will thereby be connected to the subscribers line, whereby the following circuit is closed: I battery, winding on the currentfeeding relay S2, contact I02, selector FV, line wire La, contact k, microphone M, rectifier Re2, line wire Lb, selector FV, contact I04, winding on the current-feeding relay S2 to negative.

If all the subscribers instruments are not provided with keysets, but some ofthe instruments with dials are connected to the telephone exchange, the receiving device R must also be made so as to be able to receive impulse series. The process which takes place when a subscriber replaces his micro-telephone begins for each impulse, but the relay R5, which is slow-releasing, has not time to release its armature, since contact 5| is not closed and the connecting link S therefore not disconnected. Relay RI attracts and releases its armature once for each interruption, i. e. each impulse from the dial. pulses are repeated by contact RI over wire tI to a registering device. After each impulse, relay R2 is actuated and the relays RI IR;I3 are released.

In Fig. 2, a telephone instrument T and a connecting link are shown according to Fig. 1, these parts of Fig. 2 therefore not needing be described Similarly, relays RI I-'RI6 are the same as in Fig. 2. When the registerR is busied, relay R4 attracts and contacts 4I-43 are actuated. The condenser C is thereby discharged and the grid to the electron tube G has a strong negative bias. The polarized relay RI receives The im- I scriber s line, due to the following circuit: contacts I21, I49- and I69, resistances H4, 1113,

rI2 and -rII, contact I05, selector FV, line wire Lb, rectifier Rel, resistance m, conta'ctk, line wire La, selector FV, contact-I03, resistance 12 to negative. Asthe condenser C is charged, the anode current from the anode battery +VI increases in the winding I 'onrelay RI. When the current is winding Ibalances the current in winding II, relay :RI is moved to its neutral position. Contact I12 breaks the current for relay R6, which releases its armature, whereby the ohargingof condenser C is broken. During the release time of relay 'R'I, :relay R5 receives 2I23 are actuated. 'Relay R3 receives current over contacts 2I and '85 and-closes contact 31. After compensation,- relayrRl islastly removed to its neutral position and relay R2 releases its armature. The setting of relays RI I--RI6 :is

registered in a special registering-device which is not shown, through :acircuit from contact 22 through relay R8, over contacts :II6 or I26 to,

one of the wires O -9. Relay R8 attracts itsoperated and the holding of the relays RI I-RI6,

which was before done by contact 3| or the contacts 86 and 23, is broken. Relays RI I-RI6 are released and the balance is restored. Relay RI is removed toits neutral positionand relays R2 and R8 release their armatures, whereafter a new signal can be received. i

We claim: 7 I

1. In an automatic telephone system, for use with a subscriber's line having a variable resistance connected between the branches of said line at one end of the line, of a selector signal receiving device, means connecting the other end of said subscribers line to said receiving device, in said receiving device an indicating relay influenced-by an energized electric circuit including ,cating relay when said line is connected to said current over contact 43 and resistance 15 through its winding II and is actuated so that contact I2 is closed, whereby relay R6 receives current and attracts its armature. Contacts 6I63 are actuated. Relay R1 and contact 'II are operated. Thereafter the condenser C is charged in series with the resistances T3 and r2. There is already a certain voltageover resistance 12, which voltage depends on the resistance of the subreceiving device and changing the charge of said condenser, relays and contacts releasing and dis-v connecting said energized circuit means when the anode current through said winding brings restoresaid relay to its initial condition through a variation of said impedance, and means causing the position of said operating means to represent said signal.

2. Device according to claim 1, wherein the indicating relay is a polarized relay with an intermediate position and two side positions, two windings on said relay counteracting each other, means delivering the anode current of said electron tube to one winding, means delivering a current to the other winding which is determined by the voltage of the battery at the telephone exchange and a fixed resistance.

3. For use in an automatic telephone system, having a subscribers line, a first variable resistance connected between the branches of and at one end of the line and adapted to be increased or decreased, and means to connect the other end of said subscribers line to a receiving device; said receiving device comprising in combination a second variable resistance, a fixed resistance and an indicating relay influenced by a first electric circuit including said second variable resistance, said line with said first variable resistance and said fixed resistance; an electronic valve having a plate, grid and cathode, a condenser connecting the voltage over said fixed resistance to the grid of said valve; a first winding on said relay energized by the anode current of said valve; a second winding on said relay energized in a circuit closed when'said line is connected to said receiving device; a set of relays connected to vary said second variable resistance; circuit means under control of said indicating relay for changing the polarity of charge of said condenser; auxiliary relays for disconnecting said circuit means when thevalve anode current through said first winding brings said indicating relay to either its operating or releasing condition and connecting said set of relays under control of said indicating relay; a signal over said subscribers line to said receiving device produced by varying said first resistance causing said indicating relay to actuate selected ones of said set of relays to vary said second variable resistance to compensate the variation of said first variable resistance and means on said relays of said set to indicate the signal.

4. In an automatic telephone system according to claim 3, said indicating relay being a polarized relay the armature of which has a rest position and two side positions; said set of relays containing two relay chains one being operated by said indicating relay in one of its side positions to increase said second variable resistance and the other being operated by said indicating relay in the other of its side position to decrease said second variable resistance.

ERIC ARVID ERICSSON. ERIK 'WALDEMAR HULLEGARD. ANTON CHRISTIAN JACOBAEUS References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 22,794 Deakin Oct. 1, 1946 1,242,009 Lundell Oct. 2, 1917 1,459,859 Powell June 26, 1923 1,736,283 Gardner Nov. 19, 1929 1,809,019 Hewett Apr. 7, 1931 1,952,368 Gardner Mar. 27, 1934 1,982,290 Gardner Nov. 27, 1934 2,360,751 Ziebolz Oct. 17, 1944 2,440,249 Deakin Apr. 27, 1948 2,441,269 Hartig May 11, 1948 

